1. Field of the Invention
The present invention relates to a range sensor and a range image sensor.
2. Related Background Art
A TOF (Time-Of-Flight)-type range image sensor (range sensor) is known (see, for example, T. Y. Lee et al., “A 192×108 pixel ToF-3D image sensor with single-tap concentric-gate demodulation pixels in 0.13 μm technology,” Proceedings of the 2011 IEEE International Electron Devices Meeting, Dec. 5-8, 2011, pp. 8.7.1-8.7.4). The range image sensor described in this literature includes a charge generating region configured to generate charges in response to incident light, a charge collecting region disposed inside the charge generating region so as to be surrounded by the charge generating region, a charge discharging region disposed outside the charge generating region so as to surrounds the charge generating region, an inside gate electrode disposed on the charge generating region and configured to cause charges to flow from the charge generating region into the charge collecting region in response to an input signal, and an outside discharge gate electrode disposed on the charge generating region and configured to cause charges from the charge generating region into the charge discharging region in response to an input signal. The charge collecting region is disposed at the center portion of the polygonal pixel region, and the charge discharging region is disposed around the entire pixel region. Because of a potential difference applied between the inside gate electrode and the outside discharge gate electrode, a potential gradient is formed across regions immediately below the inside gate electrode and the outside discharge gate electrode. Because of this potential gradient, charges generated in the charge generating region migrate to the charge collecting region or charge discharging region.